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Comet LINEAR Graces the Northern Sky

Comet LINEAR (C/2006 VZ13) is currently passing near the handle of the Big Dipper. The marks on this chart show where the comet lies at 0h UT on the specified date. This takes place on the preceding evening or afternoon in North America.

For instance, 11 p.m. PDT corresponds to 6h UT on the next day. So people on the West Coast looking for Comet LINEAR after the sky gets fully dark on July 10th should look ¼ of the way from the tick labeled Jul 11 to the tick for Jul 12.

Click on the image above for a detailed PDF chart that can be downloaded and printed for use under the stars.

S & T Illustration

Comet LINEAR (C/2006 VZ13), now crossing through Draco and Boötes, has far exceeded expectations. It was originally predicted to peak in brightness around magnitude 10, a pleasant spectacle for people who enjoy viewing faint comets through telescopes. But the latest magnitude estimates range from 7.5 to 8.0, making it an easy sight through 10×50 binoculars in a dark, transparent sky.

As of July 10th, the comet appears as a bright, round fuzzball roughly 8' across, with little hint of a tail. It will probably peak in brightness shortly after July 14th, when it comes nearest to Earth. Then it should fade gradually until perihelion, its closest approach to the Sun, on August 10th. But it will be disappearing into the evening twilight by the end of July.

Comet LINEAR makes two close approaches to bright deep-sky objects, which should yield excellent photo-opportunities. On the night of July 13-14, people in Asia will see it pass just 12' from the beautiful lenticular galaxy NGC 5866, sometimes called Messier 102. And on July 22-23, for observers in Europe, it pases 22' from Messier 3, one of the sky's brightest globular star clusters.

14 thoughts on “Comet LINEAR Graces the Northern Sky”

After looking at the jet porpultion labortory website it seems like the comet will come extrodanarily close to earth from Jan 23-25 2009. Does this mean that it will be bright and if so will it be visible to the naked eye from New York? Jeremy

“After looking at the jet porpultion labortory website it seems like the comet will come extrodanarily close to earth from Jan 23-25 2009.”

The answer is that the proximity is just a perspective effect. In fact, the distance (displayed on that page) is more than 5.5 Astronomical Units, or 500,000,000 miles. If you move the slider at the right-hand edge up and down, you’ll see that the comet is actually far below the plane of Earth’s orbit.

“It will probably peak in brightness shortly after July 14th, when it comes nearest to Earth. Then it should fade gradually until perihelion, its closest approach to the Sun, on August 10th.”

Why is it that the comet is actually peaking when close to Earth? Agree, that the Earth-Comet distance is important in visual brightness, but isnt the Sun-Comet distance important in the intrinsic brightness? So what does the magnitude of a comet actually depend upon?

Amar asked: “Why is it that the comet is actually peaking when close to Earth? … isn’t the Sun-Comet distance also important in the intrinsic brightness?”

Yes, both distances are important. If the comet stayed the same size and consistency, then its brightness would be inversely proportional to the comet-Earth distance times the comet-Sun distance. In other words, both distances would have equal importance.

In fact, comets generally swell up as they approach the Sun, so the comet-Sun distance is even more important than the comet-Earth distance. (Nobody can predict what any given comet will do, which is why I keep saying “generally” and “probably.”)

However, the comet happens to be passing unusually close to Earth right now, just 0.58 a.u. By perihelion, we’ll be 1.22 a.u. from the comet — more than twice as far. Meanwhile, the comet-Sun distance is increasing very slowly, from 1.13 a.u. right now to 1.02 a.u. at perihelion. Such a small change won’t have a tremendous effect.

The reason the comet-Earth distance is changing so fast is that we’re on completely different orbits, rushing past each other like cars on opposite sides of a highway. But the comet is swinging around the Sun, tracing a nearly circular shape as it does so. Play around with that JPL Java app and you’ll see what I mean.

On the same page you can view an image of the comet.
I waited until I could image it from the backside of my house (i.e. about 1am). By 4am I had converted all FITS frames to TIFF, created the animation in Flash, stacked the images, processed them and obtained the image. So it’s been nearly a whole-night marathon Note how fast the comet moved in just 26 minutes. In the image, the tail of the comet is also visible.

I really enjoyed reading your latest news on Comet Linear.Thank you for putting it on your web sight.Oh, and just what did I miss. I have been using “skytonight.com” for months now but did it change back to “skyandtelescope.com”? Please clue me in.

Joseph Caruana’s movie is really quite something — make sure you check it out. The comet certainly is moving along at a good clip right now; it changes position with respect to the stars in just a few minutes.

As for the website name, yes we’ve changed the “official” name back to SkyandTelescope.com. But Skytonight.com will continue to work for the foreseeable future.

Traditionally, since the days when all comets were detected by peering through a telescope’s eyepiece, comets have been named after their discoverers. Even back then, this caused confusion since many people discovered more than one comet. So comets have always also been designated by the year of discovery.

Naming comets after discoverers still continues for tradition’s sake, but this is increasingly meaningless in an age when the great majority of comets are found by automated sky surveys. So comet specialists use the formal designation instead — which in this case is C/2006 VZ13.

As for our charts, they’re produced by a proprietary star-charting program written by Roger Sinnott. It’s used to produce all of the charts that we run online, in our magazines, and all star atlases since the Second Edition of Sky Atlas 2000.0. You’ll note that the style of the comet chart is nearly identical to the Pocket Sky Atlas.

But the real secret isn’t the program — it’s old-fashioned elbow grease. First I spent a couple of hours trying different scales and projections, figuring out how many stars to plot and which deep-sky objects to include. Then I spent a couple of minutes running our charting program. And then I gave the output to Gregg Dinderman, illustrator extraordinaire, and he spent a couple more hours moving labels so they wouldn’t lie atop important stars, adding leader lines when necessary, and making sure that everything matched our standard style.

I’m new using the computer so I’m just learning. I enjoyed the article on Comet Linear and was able to open up JPL’s web site showing the comets orbit and being able to rotate them left and right. That’s where the problem is. Since then I have NOT been able to open the orbit diagran page and I don’t know why! I really enjoyed looking at the orbits of the different comets, so much that I e-mailed JPL to see if they could help me get the page to open. NO REPLY YET.Maybe you or Fred Schaaf could help or stear me in the right direction. Please reply.